It does not have to be a physical leash (like a plug or cable), proximity (rfid, magnetic etc) might work better as there is nothing to get tangled up. Say an ankle bracelet or something attached to your shoe.
The downside is yet another electronic component that might break.

The most important question then is if such a product would appear, what would be the proper OneWheel fashion response?
Diamond skull ankle bracelet? Rfid implant in foot? ("OneWheel 4 lyfe!1")

What readysetawesome said. The XR bumpers design is not quite there yet. They are better than nothing and I hope they continue working on it, but as it is now I'm pretty happy that I got float plates on as well.

Maybe the optimal design would be XR bumpers as a shell (current design) with additional "wear and tear" modular slots - say a tailguard and bottom plate that dips below the rails (so they take the contact before the rails) that you could easily replace as you wear them out.

This is close to what you end up with using the float plates. The forward edge of the float plate act as a tailguard, and the rest dips below the rails in addition to adding a quite thick layer of protection to the battery/controller when you do have that really bad smash.

As for rails, I don't like gouging out (over time) the main frame of a device that is carrying me at speed. The rail protectors are an easy way of avoiding that kind of wear. And you get the additional bonus of having the option to become a total fashion junkie now that there are color options available etc ;)

I also think that is an app issue.
If I remember correctly (I usually just look at the battery charge), if I go from hills one day to flat the next day then the range on screen will on startup be low then creep up as I ride.
If so then it means that the initial number is just a default number (or based on previous ride), you need to ride for a few minutes so that it has some more data to be able to make an estimation.

I wish the app could somehow be more clear that it the range it shows is an estimation, and let the user drill down to understand how that estimate came to be.

Same goes for the battery charge, I would like to be able to drill down to see the state of each cell.

For other sports practicing offhand seems to improve overall technique, or how the athlete resolve the situation. Fex when I coached kids in basketball we would focus on doing most of the layup training "goofy"/offhand (ex most shoot with right hand and jump off the left foot, offhand in this case would be to shoot with left hand and jump off the right foot). The "right" side picked up really fast and now we also had the added bonus of them being able to attack the basket from any angle while still being able to protect the ball, and to do so without having to think about it.

Another benefit was that overall focus got better as using offhand require more effort, and being able to focus for any length of time is something you have to train as well.
That said, I had to introduce this training in small but intense doses as they would initially fail quite a lot, and this would sour them to any type of training if I kept going.

Regarding the FlightShield, how does it hold up compared to a normal fender?
To me it seems to be less wide than say the onewheel fender, but I'm not sure this is a "problem" at all.
How does it hold up in a very sandy or wet environment?

That said, I really like that it is easy to remove, so easy to clean out anything that has jammed up between fender and wheel.

For anyone else finding this later - Support emailed me after 11 days, and then service got really fast. In my case the "on hold" was due to a problem with delivering to my address, but we managed to work that out and now I got my board.

So, slow initial response, but then fast followup as soon as the dialog had started.

For anyone else living in Scandinavia, it might be faster/easier to order a board from one of the local dealers (turns out there are a few in Denmark and Sweden).